1. Field of the Invention
This invention relates, in general, to electromechanical apparatus and, more specifically, to end winding restraint assemblies for turbine generators.
2. Description of the Prior Art
Restraint or bracing structures are used to secure the end winding conductors of turbine generators and to limit their movement or vibration due to normal and overload current conditions. Conventional bracing structures have used nonmetallic brackets rigidly connected to the core support plate or end shield. The bracing rings and the winding conductors are secured to the brackets, usually by an arrangement of glass roping around the conductors. When the temperature of the stator iron core increases, the thermal expansion pattern of the brackets tends to deflect the brackets outwardly and away from the end winding conductors. The resulting looseness between the brackets and the conductors, even when very minute, detrimentally affects the ability of the machine to withstand the large forces encountered under overload current conditions and the constant forces encountered under normal current conditions without damage to the machine.
The thermal expansion pattern of the conductors also causes the conductors to expand axially away from the stator iron core as the temperature increases. This movement also tends to increase the distance between the conductors and the brackets due to the conical configuration of the end winding conductors. Thus, the integrity of the bracing arrangement is degraded due to the movement of the conductors relative to the supporting brackets.
In addition to the above mentioned temperature responsive movements, it has been found that it is difficult to maintain the dimensions of the end shield or support plate within the tolerances necessary to properly hold the brackets in the desired location. Therefore, it is desirable, and it is an object of this invention, to provide an end winding restraint assembly for turbine generators which does not loose its ability to tightly hold the end winding conductors in place due to temperature and dimensional instability.